East Punjab
East Punjab (known simply as Punjab from 1950) was a province and later a state of India from 1947 until 1966, consisting of the parts of the Punjab Province of British India that went to India following the partition of the province between India and Pakistan by the Radcliffe Commission in 1947. The mostly Muslim western parts of the old Punjab became Pakistan's West Punjab, later renamed as Punjab Province, while the mostly Hindu and Sikh eastern parts went to India.
History
Partition of India
With the partition of the British Indian Empire, the Punjab province was to be divided in two as per the Indian Independence Act passed by the parliament of the United Kingdom.
The province as constituted under the Government of India Act 1935 ceased to exist and two new provinces were to be constituted, to be known respectively as West Punjab & East Punjab. The princely states of the Punjab region (which had not been British possessions, so could not be partitioned by the British) all acceded to the new Dominion of India and were combined into the Patiala and East Punjab States Union (PEPSU). The northeast Hill States of the Punjab Province banded together and were declared a union territory in 1950 as Himachal Pradesh.